The present invention is directed to a fluid filter and more particularly to a quick change disposable filter canister for filtering liquids.
Vending machines for dispensing liquids such as coffee or soft drinks in a cup are in wide spread use in our society. It is common to filter liquids such as water in coffee machines or soft drinks before they are dispensed by circulating the liquid through an appropriate filtering device. Such filtering devices have a limited useful life and require frequent replacement.
It is therefore very helpful and desirable to construct the filter for easy and simple removal and replacement. Thus, personnel who routinely replenish the machines with supplies could also replace the filter. Since those who restock the machines are not mechanically trained and do not carry hand tools, it has been known to construct the filtering device as an assembly which includes a permanently installed head in the machine and a disposable filter canister which can be easily installed in the head by persons without mechanical skill and without use of any hand tools.
Various filters of this type have been previously described. The known filtering devices are often complex in structure which tends to increase their cost. Moreover, the wide practice has been to provide "screw on" types of filters, similar to the familiar car oil filter, which require patience and time to align the filter and to screw it into position. The known filtering devices are typified by the following examples:
U.S. Pat. No. 3,746,171 in the name of Thomsen is directed to a filter assembly which includes a permanently installed head fixedly mounted in a machine and a replaceable filter unit. The replaceable filter unit is supported in a rotatable clamping collar. Upon rotation of the clamping column the filter unit is secured in the head. The head structure is complicated by the inclusion of a shut-off valve. The mating end of the replaceable filter is conically shaped and includes two coaxial tubular portions which define input and output ports into the canister. The canister receiving opening in the head is cylindrical but has a nonuniform diameter to fit snugly over and accommodate the replaceable filter.
Other patents which appear to be relevant to the subject matter of the present invention include: U.S. Pat. Nos. 2,563,548; 2,568,181; 2,979,208; 3,217,942; 3,313,417; 3,313,418; 3,319,791; 3,333,697; 3,347,386; 3,358,839; 3,852,196; 3,859,216; 4,051,036; 4,052,307; 4,082,673; 4,105,561; 4,268,384; 4,304,736; 4,349,438; 4,465,595; 4,495,072; 4,497,348; 4,520,950; 4,615,812; and 4,645,601. The majority of the above patents are directed to various filter assemblies, particularly to such assemblies having a removable filter cartridge that is attached to some type of head. A representative group of the patent is discussed below.
U.S. Pat. No. 2,563,548 in the name of Plante discloses a gasoline filter cartridge 33 having arms 42 received in a recess 50 on the under surface of a head. The filter is threaded onto the head.
U.S. Pat. No. 2,568,181 in the name of Zimmerman et al shows outwardly projecting lugs or fins 21 on the filter cartridge which are received above stops 39 in a cover. This invention was envisioned for use in connection with automotive engines.
U.S. Pat. No. 3,217,942, to Humbert Jr. et al discloses a filter unit which is particularly adapted for use in a gas station wherein the filter is located in a dispensing handle of a gasoline hose through which gasoline is dispensed into automotive vehicles. The replaceable filter unit has a neck portion which is in fluid communication with a discharge nozzle 22 and an annular clearance around the neck which is in communication with the incoming fluid from the hose. The replaceable filter is threadedly received and supported on the gas dispensing handle.
In the patent to Horne, U.S. Pat. No. 3,319,791, there is shown a filter cartridge secured within a head. The cartridge appears to have a reduced diameter end that is received within the filter head. The end carries several O-rings and is comprised of two unequally long concentric tubes to provide an input and an output path into the filter.
In the patent to Rosaen, U.S. Pat. No. 3,333,697, a bayonet filter which is structurally dissimilar from the filter of the present invention is disclosed.
U.S. Pat. No. 4,052,307 in the name of Humbert Jr. is directed to a universal filter mounting attachment particularly for the automotive field. This filter is of the spin-on type in which there is provided an adapter having lugs which are received in slots in the filter cartridge.
In the patent to Domnick, U.S. Pat. No. 4,105,561, there is shown a cartridge having a reduced diameter end that is received in a filter head. The cartridge is surrounded by a housing 1 as shown in FIG. 1 thereof.
In the patent to Cooper, U.S. Pat. No. 4,465,595 there is disclosed a filter cartridge in a head assembly which includes means for facilitated cartridge securement and removal. This patent deals with industrial filters which are used under high pressure and which are tightened with great force onto the head.
McMillin et al, U.S. Pat. No. 4,304,736, describes an apparatus for making and dispensing carbonated beverages. Similarly, Jeans U.S. Pat. No. 4,520,950 is directed to a beverage dispenser particularly adapted for use in the home. The patent to Sedam, U.S. Pat. No. 4,497,348, shows a portable post-mix carbonated beverage dispenser unit for which the quick-change filter of the present invention is particularly useful. The remaining patents are generally relevant to art of the present invention.
A prior filter, having the designation APS17 and provided by the assignee of the present application, comprises a filter canister having a neck and a tube that extends from the neck into the canister. The opening into the tube, at the top of the neck, is sealed from other entrances into the neck by a flexible, especially provided, flat hat, rather than a seal that is located on the neck's radial periphery.
The filter assemblies of the prior art are intricate in construction and therefore less economical. The majority are screw-on types and are somewhat more cumbersome to use. There is a present need for filter canisters with combined attributes of simplicity, reliability and inexpensiveness.